The invention relates to an ophthalmic surgical system and method including a disposable surgical microkeratome and, more particularly, to a surgical system and method for using such a device in laser in situ keratomileusis (LASIK).
In the past thirty-five years, several opthalmic surgical methods and devices have been developed and increasingly are used to change the shape of the cornea to correct vision defects, including myopia, hyperopia and astigmatism.
An early technique included a xe2x80x9cprimary keratectomyxe2x80x9d in which an anterior corneal lenticle is removed by manually pushing a blade of a microkeratome across the cornea. Then a xe2x80x9crefractive keratectomyxe2x80x9d is performed, wherein an optic correction is carved in the surface of the lenticle with a lathe similar to a contact lens lathe. The lenticle is sutured back in place on the eye. When an even and smooth cut is achieved, the best and most predictable results are obtained. However, the manual microkeratomes are difficult to use and require some skill to propel the blade across the cornea in an even and smooth manner, thereby providing varying qualities of primary keratectomies based on the skill and experience of the surgeon. As a result, the predictability of the refractive correction was minimal.
The methods and devices have evolved over the years to an automated, mechanical movement of the microkeratome blade across the cornea which provides a steady, even cut and which improves the predictability of the refractive correction. Furthermore, the lenticle is not completely severed from the cornea. Instead a flap is cut from the cornea, the back of the flap or the exposed stromal bed is sculpted in situ with a laser to provide the refractive correction, and the flap is replaced without sutures. This procedure is called laser in situ keratomileusis (LASIK). LASIK greatly improves the predictability of the amount of change in refractive correction and greatly reduces the amount of time required for the cornea to heal. In addition, the patient experiences a relative lack of discomfort from this procedure.
Unfortunately, problems still remain with some microkeratomes used to make the flap. Some existing microkeratomes still require the surgeon to estimate the length of the cut to make the flap because the cutting distance is not automated. Furthermore, generally microkeratomes are made of surgical steel which prevents the surgeon from viewing the cornea as the cutting blade oscillates and advances.
Another problem with some microkeratomes is that they are made of many small metal components which are expensive to produce and assemble. The assembled microkeratome may be less than two inches long, and individual components may be much smaller. As a result, cleaning and sterilization of the microkeratome between patients is very difficult. Sometimes the microkeratome must be at least partially disassembled and each component cleaned by hand. Therefore, the existing microkeratomes are difficult or even impossible to maintain in an acceptably sterile condition. Additionally, as one might imagine the assembly of many small parts while wearing sterile gloves is very difficult.
Some existing microkeratomes have one or more of the following problems in addition to those described above. For example, on some microkeratomes the depth of cut is determined by an adjustment plate which must be selected and added to the parts assembled before the operation. A last minute change may require the microkeratome to be disassembled, the adjustment plate changed, and then reassembled. Another problem is that some microkeratomes use a mechanical stop to halt the advance of the cutting blade, thereby stalling the motor. This damages the motor and reduces its useful life. Furthermore, some microkeratomes are relatively heavy, thus placing undue pressure on the eye and hindering precise location on the eye. Yet another problem with some microkeratomes is that a base must be attached to the eye and then a cutting device must be assembled and/or mounted thereon.
Therefore, a microkeratome which is easy to use, disposable or easy to clean, and performs a keratectomy in a consistent, smooth and reliable manner would be desirable.
The present invention provides a microkeratome and an associated opthalmic surgical system and method that overcome problems associated with the use of prior art microkeratomes. The present invention, inter alia, provides for independent control of the axial movement and transverse oscillation of a cutting blade of a microkeratome to provide a consistently high quality lamellar flap in the cornea of an eye. A preferred opthalmic surgical system includes a control assembly that powers and controls the movement of the cutting blade, which control assembly is preferably located remote from the microkeratome. This allows the microkeratome to be pre-assemblable, sterilizable, and preferably disposable. Furthermore, the microkeratome of the present invention preferably is made of a clear plastic, making the microkeratome lightweight and easy to produce and use, while allowing the surgeon to observe the cornea as the blade advances.
More particularly, one aspect of the invention provides a microkeratome for keratomileusis ophthalmic surgery having a base, a carriage mounted to the base and a cutting blade carried in the carriage. The carriage is guided for movement in an axial cutting direction and the cutting blade is movable in an oscillating motion transverse to the cutting direction. In addition, the carriage is movable in the cutting direction without imparting the oscillating motion to the cutting blade.
According to one embodiment of the invention, the movement of the carriage in the axial direction can be automated.
According to another embodiment of the invention, the carriage is connectable to an axial cable having a shaft movable within a sheath. In this embodiment the base of the microkeratome provides an axial retaining clip which engages an axial cable fitting on the cable to hold the sheath such that movement of the shaft imparts movement to the carriage relative to the base.
According to yet another embodiment of the invention, substantially all of the microkeratome is molded from a substantially transparent material.
Another aspect of the invention provides a system for keratomileusis ophthalmic surgery that provides a microkeratome for cutting a section of a cornea of an eye and a control assembly for controlling the microkeratome. The microkeratome provides a base, a carriage mounted to the base and a cutting blade carried in the carriage. The carriage is guided for movement in an axial direction. The control assembly includes an axial drive for generating linear movement and a rotary drive for generating rotational movement independently of the axial drive. The axial drive is connected to the microkeratome to impart axial movement to the carriage in an axial direction relative to the base and the rotary drive is connected to the microkeratome to impart an oscillating movement to the cutting blade transverse to the axial direction. The control assembly also includes a controller which controls the axial drive and the rotary drive.
According to one embodiment of the invention, the axial shaft is connected to the carriage with a coupling that permits the axial cable to rotate without imparting torque to the carriage.
According to another embodiment of the invention, the control assembly includes a suction device for supplying suction pressure to the microkeratome.
The suction device is connected to the microkeratome for generating a partial vacuum in a suction chamber mounted to the base to maintain a position of the base relative to an eye.
According to another embodiment of the invention, the controller stops operation of the axial drive and the rotary drive if the suction pressure drops below a predetermined value.
Yet another aspect of the invention provides a method for keratomileusis opthalmic surgery that includes linearly advancing a cutting blade of a microkeratome from an initial position in an axial direction while simultaneously oscillating the cutting blade in a direction transverse to the axial direction; stopping the linear advance and transverse oscillation of the cutting blade at an end position which is removed from the initial position; and linearly retracting the cutting blade to the initial position without imparting transverse oscillation to the blade.
According to one embodiment of the invention, stopping the linear advance and transverse oscillation of the cutting blade occurs automatically at a predetermined distance from the initial position.
According to another embodiment of the invention, the method includes selecting one of a plurality of microkeratomes which provide for respective depths of cut.
According to another embodiment of the invention, the method includes disposing of a first microkeratome following a first operation and selecting a second microkeratome for a subsequent operation.
According to yet another embodiment of the invention, the method includes automatically stopping the cutting blade when the suction device fails to maintain a predetermined level of suction pressure.
Another aspect of the invention provides a method for keratomileusis opthalmic surgery that includes connecting a disposable microkeratome to a control unit operative to drive and control a cutting action of the microkeratome; using the microkeratome to at least partially remove a section of a patient""s cornea; and discarding the microkeratome after use with a single patient.
Yet another aspect of the invention provides a microkeratome having a base, a carriage mounted to the base for movement, and a cutting blade carried by the carriage for movement therewith, and the base and carriage are formed of a molded transparent plastic material.
The foregoing and other features of the invention are hereinafter fully described and particularly pointed out in the claims, the following description and annexed drawings setting forth in detail a certain illustrative embodiment of the invention, this embodiment being indicative, however, of but one of the various ways in which the principles of the invention may be employed.